For a long time, attempts have been made to replicate biological tissue to imitate nature so that these structures can be used, firstly, as models for research and, secondly, for medical purposes in patients suffering from tissue loss. For the associated research area, the term “tissue engineering” has been established internationally.
For example, EP 1362092 B1 discloses a cell patch based on a collagen nonwoven support. The support composed of a wound-care nonwoven having collagen fibrils makes possible a culture of cells applied thereto, which partly allows self-organization thereof. The artificial tissue patch thus obtained can be used for the study of drug effects, the effect of growth factors on cell culture, or surgically as augmentation material. It is still not possible for more complex tissue structures to be obtained in this manner.
EP 0989867 B1 discloses a basic method for producing an acellularized and reseeded native collagen matrix as tissue transplant. However, the patent does not provide for active vascularization, and so the supply to the cells of the freshly produced bioartificial material is a problem.
This is overcome by the teaching of EP 1230939 B1, in which a primarily vascularized, acellularized, autologous, allogeneic or xenogeneic tissue matrix having at least one vascular branch is used in vitro or in vivo for the reseeding. However, the new, bioartificial tissue is bound to the vascular structure of the matrix taken as a basis and requires a human or animal starting matrix.
The course mostly pursued to date of providing a native extracellular matrix in acellularized form, of artifically replicating it, for example with a polymer, or of forming it from native material and of then allowing said matrix to remodel in the body or of then preseeding said matrix using an external method, limits the variability of the obtainable tissue to a large extent, since complex tissues are technically not manageable.
The modeling, or replication or new construction, of entire organs is therefore in its infancy and is limited to those organs having a not too complex tissue structure which is relatively uniform at least in certain areas. Specific results have been achieved to date in the direction of skin, intestine and bladder, as shown by DE 600 28 616 T2 for example.